1. Field of the Invention
The present invention relates to a multi-chip module and a method for mounting thereof, particularly, a multi-chip module that can be easily positioned on a printed circuit board and a method for mounting using the multi-chip module.
2. Description of the Related Art
Recently, in an electronic device such as a micro computer, it has been considered to improving operating speed and degree of integration by replacing electric distribution with optical distribution. Further, conventional electric telecommunication systems have been widely replaced with optical inter-connections that make it possible to communicate mass data at high speeds.
As an example of the above optical distribution system, it has been proposed to mount an optical multi-chip module (optical MCM, herein after) with an optical element carried thereon on a printed circuit board (Publication of unexamined patent application Nos. 1995-183570, 2000-47044, 2002-98863, 2002-365457, 2000-39531, and 2001-36197).
A multi-chip module (MCM), as well as an optical MCM, generates a large amount of heat and thus, needs to be efficiently cooled so as to operate the MCM appropriately. Additionally, after a long time usage, thermal damage is accumulated in the MCM and accordingly, it is difficult to extend the lifetime thereof.
Therefore, as a solution of the above problem, following methods are proposed:
layering a semi-conductor integrated circuit package and a heat-radiating plate alternately (Publication of unexamined patent application No. 1996-130292),
cooling a MCM by disposing a heat-conducting sheet, a heat-radiating metal plate (Publication of unexamined patent application No. 1998-321775), or a through hole (Publication of unexamined patent application No. 2002-270743), and
cooling a MCM by contacting with a heat sink disposed on a printed circuit board (Publication of unexamined patent application No. 2002-343928) are proposed.
However, in a conventional optical distribution system, mirrors, which reflect the light from the optical element installed in the optical MCM and guide it into the optical guides, are provided at each end of the optical guide on the printed circuit board. Accordingly, the optical MCM needs to be positioned in a high precision when mounting the optical MCM on the printed circuit board. Such accurate positioning makes the conventional optical distribution system expensive and thus, deteriorates productivity thereof.
In addition, a complicated process is needed for not only forming the optical guide but also for installing the reflecting mirror in the printed circuit board and accordingly, a printed circuit board having a large area cannot be manufactured with sufficient accuracy.
Further, although some methods for cooling a MCM are proposed in the publications of unexamined patent application Nos. 1996-130292, 1998-321775, 2002-270743, and 2002-343928, some of them are too complicated and others are insufficient to cool the MCM so that the MCM operates normally.